Thanks both for information.Where is your interview? Unless you are at a very quiet consulate like Sydney it's generally a bad idea. Even if your embassy allows you to delay you won't be able to choose the new date, you'll have to take what they give you. Someone here ended up with something like a 10-month delay in DV2015, others have been unsuccessful in getting new dates. Then again it seems Sydney is easy to reschedule. May I ask why you want to delay?
My interview will hold on Hong Kong Asia.
May be I will try to contact embassy first.